====== Ebola in West Africa, 2014-15 ======

I recently read a story, [[http://www.wired.com/2015/07/ebolas-not-done-west-africa/ | Ebola's not done with West Africa]].  It's sad to see that the epidemic is still killing people.  I've been [[.:model:start | constructing a model]] of the disease spread.  Unfortunately, it [[.:forecasts:start | forecasts]] the epidemic won't be officially over for another year:

<div round box center centeralign 500px>

<phpinc=science/ebolamodel/tfinalurl.php>

On <phpinc=science/ebolamodel/tfinalbest.php> ± <phpinc=science/ebolamodel/tfinalerr.php> days\\
(probably between <phpinc=science/ebolamodel/tfinallo.php> and <phpinc=science/ebolamodel/tfinalhi.php>).

(With an error margin of many days it's clearly ridiculous for the countdown timer to show hours, minutes, and seconds.  But including them reflects the sense of urgency I feel --- I look forward eagerly to the end of this epidemic and hope it comes much sooner than my forecast!)
</div>

But take that with a grain of salt --- [[wp>Extrapolation | extrapolations]] like this are notoriously unreliable.  Watch a history of past predictions since January 2015 as I refined my model and acquired new data:

{{ http://www.zoology.ubc.ca/~rikblok/ebolamodel/animate.gif | Past predictions }}

What may be more meaningful and interesting are some other insights from the model.  In order to get it to fit the data well, I had to make a couple surprising assumptions:

====== 1. Basic reproduction number ======

The [[wp>basic reproduction number]], $R_0$, measures how fast an infection is spreading.  When it's greater than one the disease is growing; when it is less than one it will die out.  According to my model, $R_0$ was dropping in early 2014 until it suddenly surged up between April and July.  I wonder how the ebola epidemic escaped containment between April and July 2014?

{{ http://www.zoology.ubc.ca/~rikblok/ebolamodel/latest_plotr0firstderiv.png | Basic reproduction number }}

Read more about how I calculate the [[.:parameters:start&#basic_reproduction_number | basic reproduction number]].

====== 2. Case fatality rate ======

The [[wp>case fatality rate]], $CFR$, measures the risk of an infected person dying.  My model suggests that for hospitalized patients, $CFR_H$ dropped in half from July to November 2014.  What changed between July and November last year to improve $CFR_H$ so much?

Then $CFR_H$ dropped again in mid 2015.  Again, why?

{{ http://www.zoology.ubc.ca/~rikblok/ebolamodel/latest_plotcfrh.png | Case fatality rate }}

Read more about how I calculate the [[.:parameters:start&#case_fatality_rate | case fatality rate]].

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